Principles of fluid and electrolyte balance in surgical patients Fahad bamehriz, MD Ass.prof & Consultant Advanced laparoscopic, Robotic surgery Objectives: Revision of fluid compartments (physiology part) (fluid & substance) Identify types of intravenous fluids Prescribing fluids Electrolytes abnormalities Acid-base balance Lecture reference Principles & practice of surgery book th 5 edition By O. james Garden……. Why it is important????? Very basic requirements Daily basic requirements You will be asked to do it as junior staff To maintain patient life Theory part Intravenous fluids IV fluid is the giving of fluid and substances directly into a vein. Human Body has fluid and substances Substances that may be infused intravenously volume expanders (crystalloids and colloids) blood-based products (whole blood, fresh frozen plasma, cryoprecipitate) blood substitutes, medications. Physiological applications First part is fluid We are approximately twothirds water General information Total body water is 60% of body weight Influenced by age,sex and lean body mass Older age and female sex is less precent To calculate TBW needed: Male sex TBW= BW× 0.6 Female sex TBW= BW × 0.5 Body fluid compartments: Intracellular volume (40%) rich in water Extra cellular volume (20%) rich in water 15% constitute interstitial space and 5% the intravascular space. Fluid shifts / intakes Kidneys Guts Lungs Intracellular 40% OF BW Interstitial IV 30 litres 15% BW 5% BW 9 litres 3 litres Extracellular fluid - 12 litres Skin Second part is electrolytes Body electrolytes compartments: Intracellular volume K+, Mg+, and Phosphate (HPO4-) Extra cellular volume Na+, Cl-, Ca++, and Albumin Normal values of electrolytes HHCO3 200 Nonelectrolytes K+ 157 175 hco-3 27 150 125 Na+ 152 100 75 50 25 0 HCO3- 10 nn Ci113 K+5 Hco-3 27 HPO42-2 SO42-1 Ca2+5 Mg2+3 HHCO3 Org. acid6 Protein 16 blood plasma po43113 K+ Ca2+5 Mg2+3 Na+ 143 Ci117 HPO42-1 SO42-1 Org. acid6 protein2 interstitial fluid Na+ 14 Protein 74 Mg2+ 26 intracellular fluid Fluid shifts / intakes Kidneys Guts Lungs Intracellular 40% OF BW Interstitial IV 30 litres 15% BW 5% BW 9 litres 3 litres Extracellular fluid - 12 litres Skin EXAMPLE 1 Fluid Compartments 70 kg male: (70x 0.6) TBW= 42 L Intracellular volume = .66 x 42 = 28 L Extracellular volume = .34 x 42 = 14 L • Interstitial volume = .66 x 14 = 9 L • Intravascular volume = .34 x 14 = 5 L Daily requirements of fluid and electrolytes Fluid Requirements Normal adult requires approximately 35cc/kg/d “4,2,1” Rule l hr First 10 kg= 4cc/kg/hr Second 10 kg= 2cc/kg/hr 1cc/kg/hr thereafter Normal daily losses and requirements for fluids and electrolytes Urine Insensible losses (skin and respiratory tract) Faeces Minus endogenous Water Total Volume (ml) Na+ (mmol) K+ (mmol) 2000 700 80 -- 60 -- 300 -- 10 300 2700 -80 -70 Fluid shifts in disease Fluid loss: GI: diarrhoea, vomiting, etc. renal: diuresis vascular: haemorrhage skin: burns Fluid gain: Iatrogenic: Heart / liver / kidney failure: WHAT IS THE AMOUNT? In adults remember IVF rate = wt (kg) + 40. 70 + 40 = 110cc/hr Assumes no significant renal or cardiac disease and NPO. This is the maintenance IVF rate, it must be adjusted for any dehydration or ongoing fluid loss. Conversely, if the pt is taking some PO, the IVF rate must be decreased accordingly. Daily lytes, BUN ,Cr, I/O, and if possible, weight should be monitored in patients receiving significant IVF. Sodium requirement Na: 1-3 meq/kg/day 70 kg male requires 70-210 meq NaCl in 2600 cc fluid per day. 0.45% saline contains 77 meq NaCl per liter. 2.6 x 77 = 200 meq Thus, 0.45% saline is usually used as MIVF assuming no other volume or electrolyte issues. Potassium requirment Potassium: 1 meq/kg/day K can be added to IV fluids. Remember this increases osm load. 20 meq/L is a common IVF additive. This will supply basal needs in most pts who are NPO. If significantly hypokalemia, order separate K supplementation. Oral potassium supplementation is always preferred when feasible. Should not be administered at rate greater than 10-20 mmol/hr Calculation of osmolality Difficult: measure & add all active osmoles Easy = [ sodium x 2 ] + urea + glucose Normal = 280 - 290 mosm / kg Third part is medicine Iv fluids IV fluid forms: ????? Colloids Crystalloids Iv Fluids Colloid solutions Containing water and large proteins and molecules tend to stay within the vascular space Crystalloid solutions containing water and electrolytes. Colloid solutions - IV fluids containing large proteins and molecules - tend to stay within the vascular space and increase intravascular pressure -very expensive - Examples: Dextran, hetastarch, albumin… Crystalloid solutions Contain electrolytes (e.g.,sodium, potassium, calcium, chloride) Lack the large proteins and molecules Come in many preparations and volum Classified according to their “tonicity: ” 0.9% NaCl (normal saline), Lactated Ringer's solution isotonic, 2.5% dextrose hypotonic D5 NaCl hypertonic Type of fluid* Sodium mmol/L Potassium Chloride mmol/L mmol/L Osmolority mmom/L Weight average mol wtkd Plasma volume expansion duration hrs+ plasma 136 145 3.5 – 5.0 98 -105 280 - 300 - - 5% Dextrose 0 0 0 278 - - Dextrose 0.18% saline 30 0 30 283 0.9% “normal” saline 154 0 154 308 - 0.2 0.45%”half normal” saline 77 0 77 154 - Ringer’s lactate 130 4 109 273 - 0.2 Hartmann’s 131 5 111 275 - 0.2 Gelatine 4% 145 0 145 290 30,000 1-2 5% albumin 150 0 150 300 68,000 2-4 20% albumin - - - - 68,000 2-4 Hes 6% 130/0.4 154 0 154 308 130,000 4-8 Hes 10% 200/0.5 154 0 154 308 200,000 6-12 Normal saline fluid (NS 0.9%) (NS) — is the commonly-used term for a solution of 0.90% w/v of NaCl, about 300 mOsm/L or 9.0 g per liter Na is154 and only CL 154 No K, NO others Hartmann’s fluid One litre of Hartmann's solution contains: 131 mEq of sodium ion = 131 mmol/L. 111 mEq of chloride ion = 111 mmol/L. 29 mEq of lactate = 29 mmol/L. 5 mEq of potassium ion = 5 mmol/L. 4 mEq of calcium ion = 2 mmol/L . Ringer lactate fluid One litre of lactated Ringer's solution contains: 130 mEq of sodium ion = 130 mmol/L 109 mEq of chloride ion = 109 mmol/L 28 mEq of lactate = 28 mmol/L 4 mEq of potassium ion = 4 mmol/L 3 mEq of calcium ion = 1.5 mmol/L Osmotic / oncotic pressure Gibbs – Donnan Equilibrium Na+ Na+ PP Intracellular Interstitial Intravascular CASE FOR PRACTICE FLUID 35/KG/DAY, Na: 1-3 meq/kg/day., K: 1 meq/kg/day 70 kg male requires 2450 cc fluid per day, 70-210 meq Na 0.45% saline contains 77 meq NaCl per liter. 2.6 x 77 = 200 meq Thus, 0.45% saline is usually used as MIVF assuming no other volume or electrolyte issues. Terminologies: A solvent is the liquid where particles dissolves in (e.g. Water) that can be measured in liters and milliliters Solutes are the dissolving particles A molecule is the smallest unit with chemical identity (e.g. Water consist of one oxygen and two hydrogen atoms = water molecule) Ions are dissociated molecule into parts that have electrical charges ( e.g. NaCl dissociates into Na+ and Cl-) Cations are positively charged ions (e.g. Na+) due to loss of an electron (e-) and anions are negatively charged ions (e.g. Cl-) due to gain of an electrone (e-) Electrolytes are interacting cations and anions (e.g. H+ + Cl- = HCL [hydrochloric acid]) A univalent ion has one electrical charge (e.g. Na+). A divalent ion has two electrical charges (e.g. Ca++) Molecular weight is the sum of atomic weights of different parts of a molecule (e.g. H+ [2 atoms] + O2 [16 atoms] = H2O [18 atoms]) A mole is a measuring unit of the weight of each substance` in grams (e.g. 1 mole of Na+ = 23 grams, 1 mole of Cl- = 35 grams, 1 mole of NaCl = 58 grams). It can be expressed in moles/L, millimoles x 10-3/L, micromoles x 10-6/L of the solvent. Equivalence refers to the ionic weight of an electrolyte to the number of charges it carries (e.g. 1 mole of Na+ = 1 Equivalent, whereas 1 mole of Ca++ = 2 Equivalents). Like moles, equivalence can also be expressed in milliequivalent/L and microequivalent/L of the solvent. Osmosis is the movement of a solution (e.g. water) through a semi permeable membrane from the lower concentration to the higher concentration. Osmole/L or milliosmole/L is a measuring unit for the dissolution of a solute in a solvent Osmotic coefficient means the degree of dissolution of solutes (molecules) in a solvent (solution). For example the osmotic coefficient of NaCl is 0.9 means that if 10 molecules of NaCl are dissolved in water, 9 molecules will dissolve and 1 molecule will not dissolve. Osmolarity is the dissolution of a solute in plasma measured in liters, whereas Osmolality is the dissolution of a solute in whole blood measured in kilograms. Therefore, Osmolality is more accurate term because dissolution of a solute in plasma is less inclusive when compared to whole blood that contains plasma (90%) and Proteins (10%). Gibbs – Donnan Equilibrium refers to movement of chargeable particles through a semi permeable membrane against its natural location to achieve equal concentrations on either side of the semi permeable membrane. For example, movement of Cl- from extra cellular space (natural location) to intracellular space (unusual location) in case of hyperchloremic metabolic acidosis because negatively charged proteins (natural location in intravascular space) are large molecules that cannot cross the semi permeable membrane for this equilibrium. Tonicity of a solution means effective osmolality in relation to plasma (=285 milliosmol/L). Therefore, isotonic solutions [e.g. 0.9% saline solution] have almost equal tonicity of the plasma, hypotonic solutions [e.g. 0.45% saline solution] have < tonicity than plasma, and hypertonic [e.g. 3% saline solution] solutions have > tonicity than plasma. Abnormal Hypokalemia: Occurs when serum K+<3 mEq/L. Treatment involves KCl i.v. infusion or orally. THE MOST COMMON SURGICAL ABNORMALITY Should not be administered at rate greater than 10-20 mmol/hr Causes of hypokalaemia Reduced/inadequate intake Gastrointestinal tract losses Vomiting Gastric aspiration/drainage Fistulae Diarrhoea Ileus Intestinal obstruction Potassium-secreting villous adenomas Urinary losses Metabolic alkalosis Hyperaldosteronism Diuretic use Renal tubular disorders(e.g. bartter’s syndrome, renal tubular acidosis, amphotericin-induced tubular damage) Hyperkalemia: Diagnosis is established by ↑ serum K+>6 meq/L and ECG changes. Causes include increase K+ infusion in IVF, tissue injury, metabolic acidosis, renal failure, blood transfusion, and hemodialysis. Arrythmia is the presentation Causes of hyperkalaemia Haemolysis Rhabdomyolysis Massive tissue damage Acidosis……..ARF Management of high K Diagnosis is established by ↑ serum K+>6 meq/L and ECG changes. Treatment includes 1 ampule of D50% + 10 IU Insulin intravenously over 15 minutes, calcium exalate enemas, Lasix 20-40 mg i.v., and dialysis if needed. Sodium Excess (Hypernatremia): Diagnosis is established when serum sodium > 145mEq/L. this is primarily caused by high sodium infusion (e.g. 0.9% or 3% NaCl saline solutions). Another but rare cause is hyperaldosteronism.( What is function?) Patients with CHF, Cirrhosis, and nephrotic syndrome are prone to this complication Symptoms and sign of are similar to water excess. Causes hypernatreamia Reduced intake Fasting Nausea and vomiting Ileus Reduced conscious level Increased loss Sweating (pyrexia, hot environment) Respiratory tract loss (increased ventilation, administration of dry gases) Burns Inappropriate urinary water loss Diabetes insipidus (pituitary or nephrogenic) Diabetes mellitus Excessive sodium load (hypertonic fluids, parenteral nutrition) Management of HN Diagnosis is established when serum sodium > 145mEq/L. Treatment include water intake and ↓ sodium infusion in IVF (e.g. 0.45% NaCl or D5%Water). Sodium Deficit (Hyponatremia): Causes are hyperglycemia, excessive IV sodium-free fluid administration (Corrected Na= BS mg/dl x 0.016 + P (Na) ) can be volum over load, normo, low Hyponatremia with volum overload usually indicates impaired renal ability to excrete sodium Treatment of hypo Na Administering the calculated sodium needs in isotonic solution In severe hyponatremia ( Na less than 120meq/l): hypertonic sodium solution Rapid correction may cause permanent brain damage duo to the osmotic demyelination syndrom Serum Na sholud be increased at a rate not exceed 10-12meq/L/h. Water Excess: caused by inappropriate use of hypotonic solutions (e.g. D5%Water) leading to hypoosmolar hyponatremia, and Syndrome of inappropriate anti-diuretic hormone secretion (SIADH) Look for SIADH causes :malignant tumors, CNS diseases, pulmonary disorders, medications, and severe stress. The role of ADH: = urinary concentration = secreted in response to osmo; = secreted in response to vol; ADH acts on DCT / CD to reabsorb water Acts via V2 receptors & aquaporin 2 Acts only on WATER ADH ADH Symptoms of EW Symptoms of water excess develop slowly and if not recognized and treated promptly, they become evident by convulsions and coma due to cerebral edema Signs of hypo / hypervolaemia: Signs of … Volume depletion Volume overload Postural hypotension Tachycardia Absence of JVP @ 45o Decreased skin turgor Dry mucosae Supine hypotension Oliguria Organ failure Hypertension Tachycardia Raised JVP / gallop rh Oedema Pleural effusions Pulmonary oedema Ascites Organ failure Treatment of EW water restriction and infusion of isotonic or hypertonic saline solution In the SIADH secretion. Diagnosis of SIADH secretion is established when urine sodium > 20 mEq/L when there is no renal failure, hypotension, and edema. Treatment involves restriction of water intake (<1000 ml/day) and use of ADH- Antagonist (Demeclocycline 300600 mg b.i.d). Water Deficit: the most encountered derangement of fluid balance in surgical patients. Causes include Bleeding, third spacing, gastrointestinal losses, increase insensible loss (normal ≈ 10ml/kg/day), and increase renal losses (normal ≈ 500-1500 ml/day). Symptoms and Signs of WD Symptoms of water deficit include feeling thirsty, dryness, lethargy, and confusion. Signs include dry tongue and mucous membranes, sunken eyes, dry skin, loss of skin turgor, collapsed veins, depressed level of conciousness, and coma. Signs of hypo / hypervolaemia: Signs of … Volume depletion Volume overload Postural hypotension Tachycardia Absence of JVP @ 45o Decreased skin turgor Dry mucosae Supine hypotension Oliguria Organ failure Diagnosis of WD Diagnosis can be confirmed by ↑ serum sodium (>145mEq/L) and ↑ serum osmolality (>300 mOsmol/L) Tratment of WD If sodium is > 145mEq/L give 0.45% hypotonic saline solution, if sodium is >160mEq/L give D5%Water cautiously and slowly (e.g. 1liter over 2-4 hours) in order not to cause water excess. Bleeding should be replaced by IVF initially then by whole blood or packed red cells depending on hemoglobin level. Each blood unit will raise the hemoglobin level by 1 g. Third spacing replacement can be estimated within a range of 4-8 ml/kg/h. Gastrointestinal and intraoperative losses should be replaced cc/cc. IVF maintenance can be roughly estimated as 4/2/1 rule. Hypercalcemia: Diagnosis is established by measuring the free Ca++ >10mg/dl. In surgical patients hypercalcemia is usually caused by hyperparathyroidism and malignancy. Symptoms of hypercalcemia may include confusion, weakness, lethargy, anorexia, vomiting, epigastric abdominal pain due to pancreatitis, and nephrogenic diabetes Management of high Ca Diagnosis is established by measuring the free Ca++ >10mg/dl. Treatment includes normal saline infusion, and if CA++>14mg/dl with ECG changes additional diuretics, calcitonin, and mithramycin might be necessary Hypocalcemia: Results from low parathyroid hormone after thyroid or parathyroid surgeries, low vitamin D, pseudohypocalcemia (low albumin and hyperventilation). Other less common causes include pancreatitis, necrotizing fascitis, high output G.I. fistula, and massive blood transfusion. Symptoms and signs of low Ca may include numbness and tingling sensation circumorally or at the fingers’ tips. Tetany and seizures may occur at a very low calcium level. Signs include tremor, hyperreflexia, carpopedal spasms and positive Chvostek sign. Treatment of low Ca Treatment should start by treating the cause. Calcium supplementation with calcium gluconate or calcium carbonate i.v. or orally. Vitamin D supplementation especially in chronic cases. Hypomagnesaemia: The majority of magnesium is intracellular with only <1% is in extracellular space. It happens from inadequate replacement in depleted surgical patients with major GI fistula and those on TPN. Magnesium is important for neuromuscular activities. (can not correct K nor Ca) In surgical patients hypomagnesaemia is a frequently missed common electrolyte abnormality as it causes no major alerting Hypermagnesaemia: Mostly occur in association with renal failure, when Mg+ excretion is impaired. The use of antacids containing Mg+ may aggravate hypermagnesaemia. Treatment includes rehydration and renal dialysis. Hypophosphataemia: This condition may result from : -inadequate intestinal absorption, -increased renal excretion, -hyperparathyroidism, - massive liver resection, and -inadequate replacement after recovery from significant starvation and catabolism. Management of low phos Hypophosphataemia causes muscle weakness and inadequate tissue oxygenation due to reduced 2,3diphosphoglycerate levels. Early recognition and replacement will improve these symptoms. Hyperphosphataemia: Mostly is associated with renal failure and hypocalcaemia due to hypoparathyroidism, which reduces renal phosphate excretion. Prescribing fluids: Crystalloids:( iso, hypo, hypertonic) 0.9% saline - not “ normal “ ! 5% dextrose 0.18% saline + 0.45% dextrose Others Colloids: blood plasma / albumin synthetics The rules of fluid replacement: Replace blood with blood Replace plasma with colloid Resuscitate with colloid Replace ECF depletion with saline Rehydrate with dextrose Principles of surgical care 670 Intravascular volum 786 1000 Extracellular fluid Intracellular fluid 260 214 70 5% dextrose 4.5% albumin 0.9% NaCl ringer,s lactate Hartmann’s solution Starches Gelofusine haemaccel Guidelines for fluid therapy Crystalloids & colloids 2 litres of blood 30 litres 9 litres 3 litres Crystalloids & colloids 30 litres 9 litres 5 litres Crystalloids & colloids 2 litres of colloid 30 litres 9 litres 3 litres Crystalloids & colloids 30 litres 9 litres 5 litres Crystalloids & colloids 29 litres 8 litres 7 litres Crystalloids & colloids 2 litres of 0.9% saline 30 litres 9 litres 3 litres Crystalloids & colloids 30 litres 9 litres 5 litres Crystalloids & colloids 29 litres 10.5 litres 4.5 litres Crystalloids & colloids 2 litres of 5% dextrose 30 litres 9 litres 3 litres Crystalloids & colloids 31 litres 9.7 litres 3.3 litres How much fluid to give ? What is your starting point ? Euvolaemia ? ( normal ) Hypovolaemia ? ( dry ) Hypervolaemia ? ( wet ) What are the expected losses ? What are the expected gains ? What are the expected losses ? Measurable: urine ( measure hourly if necessary ) GI ( stool, stoma, drains, tubes ) Insensible: sweat exhaled What are the potential gains ? Oral intake: fluids nutritional supplements bowel preparations IV intake: colloids & crystalloids feeds drugs Examples: What follows is a series of simple - and some more complex fluid-balance problems for you Answers are in the speakers notes. Case 1: A 62 year old man is 2 days post-colectomy. He is euvolaemic, and is allowed to drink 500ml. His urine output is 63 ml/hour: 1. How much IV fluid does he need today ? 2. What type of IV fluid does he need ? Case 2: 3 days after her admission, a 43 year old woman with diabetic ketoacidosis has a blood pressure of 88/46 mmHg & pulse of 110 bpm. Her charts show that her urine output over the last 3 days was 26.5 litres, whilst her total intake was 18 litres: 1. How much fluid does she need to regain a normal BP ? 2. What fluids would you use ? Case 3: An 85 year old man receives IV fluids for 3 days following a stroke; he is not allowed to eat. He has ankle oedema and a JVP of +5 cms; his charts reveal a total input of 9 l and a urine output of 6 litres over these 3 days. 1. How much excess fluid does he carry ? 2. What would you do with his IV fluids ? Case 4: 5 days after a liver transplant, a 48 year old man has a pyrexia of 40.8oC. His charts for the last 24 hours reveal: urine output: 2.7 litres drain output: 525 ml nasogastric output: 1.475 litres blood transfusion: 2 units (350 ml each) IV crystalloid: 2.5 litres oral fluids: 500 ml Case 4 cont: On examination he is tachycardic; his supine BP is OK, but you can’t sit him up to check his erect BP. His serum [ Na+ ] is 140 mmol/l. How much IV fluid does he need ? What fluid would you use ? Acid-Base balance Normal physiology Hydrogen ion is generated in the body by: 1-Protein and CHO metabolism (1meq/kg of body weight) 2-Predominant CO2 production It is mainly intracellular PH depends on HCO3 CO2 Normal physiology PH = log 1/[H+] Normal PH range = 7.3 – 7.42 PH<7.3 indicates acidosis PH>7.42 indicates alkalosis Buffers 1- Intracellular Proteins Hemoglobin Phosphate 2- bicarbonate/carbonic acid system H+ + HCO3 ↔ H2CO3 ↔ H2O + CO2 The main MECHANISM HOW DO YOU READ A/VBG PH = 7.3-7.4 Partial pressure of CO2 in plasma (Pco2) = 40 mmHg Partial pressure of O2 in plasma (Po2) = 65 mmHg Bicarbonate concentration (HCO3) = 24 mEq/L O2 Saturation ≥ 90% Base Excess 2.5 mEq/L (<2.5 metabolic acidosis, >2.5 metabolic alkalosis) Anion Gap (Na+ - [HCO3+Cl]) = 12 (>12 met. acidosis, < 12 met. alkalosis) Anion Gap AG= Cations (NA+ K) – Anions (CL + HCO3) Normal value is 12 mmol Metabolic acidosis with: 1-Normal AG (Diarrhea, Renal tubular acidosis) 2-High AG , -Endogenous(Renal failure, diabetic acidosis, sepsis) -Exogenous (aspirin, methanol, ethylene glycol ) Acid-base disorders Metabolic acidosis Respiratory acidosis Respiratory alkalosis Metabolic alkalosis Causes of metabolic acidosis Lactic acidosis Shock (any cause) Severe hypoxaemia Severe haemorrhage/anaemia Liver failure Accumulation of other acids Diabetic ketoacidosis Acute or chronic renal failure Poisoning (ethylene glycol, methanol,salicylates) Increased bicarbonate loss Diarrhoea Intestinal fistulae Causes of metabolic alkalosis Loss of sodium, chloride, water: vomiting, NGT, LASIX hypokalaemia Causes of respiratory acidosis Common surgical causes of respiratory acidosis Central respiratory depression Opioid drugs Head injury or intracranial pathology Pulmonary disease Severe asthma COPD Severe chest infection Causes of respiratory alkalosis Causes of respiratory alkalosis Pain apprehension/hysterical hyperventilation Pneumonia Central nervous system disorders(meningitis, encephalopathy) Pulmonary embolism Septicaemia Salicylate poisoning Liver failure Type of A- B disorder Acute (Uncompensated) Chronic (Partially compensated) PH PH PCO2 HCO3 PCO2 HCO3 ↑ Respiratory acidosis ↓↓ ↑↑ Normal ↓ ↑↑ Respiratory alkalosis ↑↑ ↓↓ Normal ↑ ↓↓ ↓ Metabolic acidosis ↓↓ Normal ↓↓ ↓ ↓ ↓ Metabolic alkalosis ↑↑ Normal ↑↑ ↑ ↑ ↑